A conventional unit apparatus like a distribution board has no partition between units and thus becomes in a communicated state; and accordingly, an arc gas discharged from a device such as a breaker during a short-circuit fault stretches to the upper and lower units and the fault is likely to be enlarged.
As shown in FIG. 10 and FIG. 11, a conventional unit apparatus like a control center is structured such that there is not a partition structure which is for shielding between units 1 on the unit 1 side, a partition plate 4 which is for partitioning between the units 1 is previously provided on the housing 3 side at a position matched with the height of each unit 1, a unit chamber 5 is constituted on the housing 3 side separately from constituent components of the unit 1 on the unit 1 side, and an arc gas discharged from a device 2 such as a breaker is shielded.
Thus, the partition plate 4 needs to be separately provided on the housing 3 side in addition to the constituent components of the unit 1; and accordingly, it causes increases in the number of components and an assembly work time. Further, when a change in stacking and a change in size of the unit 1 occur, the partition plate 4 provided on the housing 3 side also needs a repartition work in accordance with the change in stacking of the unit 1 and it causes an increase in cost.